上硬下软型膨胀土路堑滑塌成因与处治

Causes and Treatment of Dual-structure Cutting Collapse in Expansive Soil Area

上覆岩层下伏膨胀土型路堑边坡兼具特殊性质土、不稳定地层结构、开挖卸荷等不利因素,给岩土工作者提出了新挑战。依托河北坝上某路堑滑塌病害处治工程,在分析上硬下软型膨胀土边坡变形破坏过程的基础上,提出了针对该类边坡的处治方案。取得的主要结论有:(1)影响上硬下软型膨胀土路堑滑塌稳定性的因素中,膨胀土“失水收缩、遇水膨胀”引发的裂隙发展是控制性因素,上硬下软的不稳定地层结构、开挖引起的应力条件变化是次要因素,气候环境的变化则是直接诱发因素;(2)案例分析表明,由于受上覆岩土层自重荷载影响,上硬下软型膨胀土边坡滑塌面较深,非浅表层滑动;(3)春融期是北方膨胀土边坡失稳的重要窗口期,应加强监测和防护;(4)实践表明桩板式支挡结构+柔性防护方案适用于上硬下软型膨胀土边坡滑塌病害的治理,实用效果良好。

The expansive soil cutting slope under overlying strata has some unfavorable factors such as special soil properties,unstable formation structure,excavation and unloading,which presents new challenges to geotechnical workers.Relying on the treatment project of a cutting collapse in Bashang,Hebei Province,based on the analysis of the deformation and failure process of the upper hard and lower soft expansive soil slope,the treatment scheme for this kind of slope is proposed.The main conclusions are as follows:(1)Among the factors affecting the stability of the upper hard and lower soft expansive soil cutting,the crack development caused by the“shrinkage due to water loss and expansion due to water”of the expansive soil is the controlling factor,the unstable formation structure of the upper hard and lower soft,and the change of stress conditions caused by excavation are the secondary factors,and the change of climate environment is the direct inducing factor;(2)The case study shows that due to the influence of the self-weight load of the overlying rock and soil layer,the upper hard and lower soft expansive soil slope has a deep sliding surface and is not a shallow sliding surface;(3)The spring thawing period is an important window period for the instability of the expansive soil slope in the north,and the monitoring and protection should be strengthened;(4)The practice shows that the pile-plate retaining structure+flexible protection scheme is applicable to the treatment of the collapse disease of the upper hard and lower soft expansive soil slope,and the practical effect is good.